What do you think of the fearful War of Dwarves and Goblins, to which the Dwarves of the Iron Hills came last, nine years after Thror Nain's uncle was killed and six years into the war?Now that's what I call a plothole.As I've written in my reply to SirDennis, Thorin did plan a massive alliance, and was talked out of it by Gandalf. Who knows, perhaps the wizard wanted an expedition just large enough to distract Smaug while not raising the Necromancer's alert? After all, that was not the only operation in the East of Wilderland theatre...And if nothing else, just think of the logistics. A messenger to the Iron Hills would have to pass through the Grey Mountains, or Dol Guldur, of next to Smaug - not a very easy task to accomplish. And how and where would they plan their rendezvous?